U.S. patent number 11,329,538 [Application Number 16/855,013] was granted by the patent office on 2022-05-10 for rotor of rotary electric machine.
This patent grant is currently assigned to Toshiba Industrial Products and Systems Corporation, TOSHIBA INFRASTRUCTURE SYSTEMS & SOLUTIONS CORPORATION. The grantee listed for this patent is Toshiba Industrial Products and Systems Corporation, TOSHIBA INFRASTRUCTURE SYSTEMS & SOLUTIONS CORPORATION. Invention is credited to Masaaki Matsumoto, Makoto Matsushita, Katsutoku Takeuchi, Yuji Yamamoto.
United States Patent |
11,329,538 |
Takeuchi , et al. |
May 10, 2022 |
Rotor of rotary electric machine
Abstract
According to one embodiment, in a lateral cross section, a rotor
core includes a plurality of layers of barrier regions formed to be
arranged in a radial direction with intervals in each magnetic
pole. Each barrier region includes a flux barrier extending from
near a part of an outer circumferential surface through d axis to
near another part thereof. At least a flux barrier of a barrier
region provided at an outermost circumferential surface side is
filled with a nonmagnetic conductive material. A barrier-side edge
on a side of the central axis, which defines the flux barrier of
the barrier region provided in an outermost circumferential surface
side is located within a range of 0.55<2a/R.sup.2 <0.84.
Inventors: |
Takeuchi; Katsutoku (Kokubunji,
JP), Matsushita; Makoto (Fuchu, JP),
Yamamoto; Yuji (Mie, JP), Matsumoto; Masaaki
(Mie, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
TOSHIBA INFRASTRUCTURE SYSTEMS & SOLUTIONS CORPORATION
Toshiba Industrial Products and Systems Corporation |
Kawasaki
Kawasaki |
N/A
N/A |
JP
JP |
|
|
Assignee: |
TOSHIBA INFRASTRUCTURE SYSTEMS
& SOLUTIONS CORPORATION (Kawasaki, JP)
Toshiba Industrial Products and Systems Corporation
(Kawasaki, JP)
|
Family
ID: |
72913357 |
Appl.
No.: |
16/855,013 |
Filed: |
April 22, 2020 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20200343798 A1 |
Oct 29, 2020 |
|
Foreign Application Priority Data
|
|
|
|
|
Apr 23, 2019 [JP] |
|
|
JP2019-082034 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02K
19/14 (20130101); H02K 1/246 (20130101); H02K
2213/03 (20130101) |
Current International
Class: |
H02K
19/14 (20060101); H02K 1/24 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
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2001-186735 |
|
Jul 2001 |
|
JP |
|
2002-199675 |
|
Jul 2002 |
|
JP |
|
2003-009484 |
|
Jan 2003 |
|
JP |
|
4098939 |
|
Jun 2008 |
|
JP |
|
4588255 |
|
Nov 2010 |
|
JP |
|
2017-50918 |
|
Mar 2017 |
|
JP |
|
2018-61404 |
|
Apr 2018 |
|
JP |
|
2018-68090 |
|
Apr 2018 |
|
JP |
|
WO 2018/051690 |
|
Mar 2018 |
|
WO |
|
Primary Examiner: Desai; Naishadh N
Attorney, Agent or Firm: Oblon, McClelland, Maier &
Neustadt, L.L.P.
Claims
What is claimed is:
1. A rotor of a rotary electric machine, comprising: a shaft
rotatable around a central axis; and a rotor core comprising a
plurality of magnetic poles arranged in a circumferential direction
around the central axis, and coaxially fixed to the shaft, when, in
a lateral cross section of the rotor core, normal to the central
axis, an axis extending through a boundary between adjacent
magnetic poles and the central axis is defined as a d axis and an
axis magnetically intersecting perpendicular to the d axis is
defined as a q axis, the rotor core comprising a plurality of
layers of barrier regions formed to be arranged in a radial
direction with intervals respectively therebetween, in the
plurality of magnetic poles, and the plurality of barrier regions
each comprising a flux barrier extending from near a part of an
outer circumferential surface of the rotor core through the d axis
to near another part of the outer circumferential surface, a first
bridge portion formed of an iron core located between one end of
the flux barrier and the outer circumferential surface and a second
bridge portion formed of an iron core located between an other end
of the flux barrier and the outer circumferential surface, and at
least a flux barrier of a barrier region provided at an outermost
circumferential surface side being filled with a nonmagnetic
conductive material, and when a radius of a circle circumscribed on
the outer circumferential surface is represented by R and an
equation of a hyperbola X coordinates and Y coordinates of which
are two q axes adjacent to each other in the circumferential
direction is defined as xy-a=0, a barrier-side edge on a side of
the central axis, which defines the flux barrier of the barrier
region provided in an outermost circumferential surface side being
located within a range of 0.55<2a/R.sup.2 <0.84.
2. The rotor of claim 1, wherein the barrier-side edge on the side
of the central axis is located within a range of 0.55<2a/R.sup.2
<0.78.
3. The rotor of claim 1, wherein each of the plurality of barrier
regions is curved in a convex manner toward the central axis.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority
from Japanese Patent Application No. 2019-082034, filed Apr. 23,
2019, the entire contents of which are incorporated herein by
reference.
FIELD
Embodiments described herein relate generally to a rotor of a
rotary electric machine.
BACKGROUND
A synchronous reluctance motor is proposed as a rotary electric
machine. A rotor of the reluctance motor is provided with a flux
barrier formed of a nonmagnetic material. In such a reluctance
motor, torque is produced by creating salient polarity due to the
difference in magnetic permeability between the rotor core and the
flux barrier. A typical example of the nonmagnetic material (whose
relative permeability is about 1) is air. For this reason, in many
examples of the inverter-driven synchronous reluctance motor, the
flux barrier is formed as a cavity (in which no member is
provided).
Meanwhile, aluminum, copper and the like are nonmagnetic materials,
but they are conductive materials as well. For this reason, by
filling a flux barrier with aluminum, copper or the like, a
secondary conductor can be formed. More specifically, induction
torque is produced in an asynchronous state (in which the
rotational speed of the rotating field of the stator and the
physical rotational speed of the rotor do not agree with each
other, thereby causing sliding), and thus it is possible to realize
a self-starting synchronous reluctance motor, which can be
line-driven.
The self-starting synchronous reluctance motor does not require an
inverter for drive, and therefore it can improve the efficiency as
the entire motor drive system and can also reduce the system
cost.
However, the conventional technology still entails such drawbacks
that sufficient induction torque cannot be ensured and therefore a
starting performance which satisfies the required specification
cannot be obtained. For example, in a reluctance motor having a
large moment of inertia, it may not be unable to accelerate it to
the synchronous speed (it cannot be synchronized) if the loads of
outputs are the same.
In order to enlarge induction torque, it is necessary to enlarge
the cross section of the secondary conductor and to decrease the
secondary resistance. However, when the area of the secondary
conductor is enlarged, the magnetic balance of the rotor is
disturbed and the salient polarity of the rotor is decreased. That
is, even if synchronization is achieved, the torque and the
power-factor are low while being driven synchronously, thus making
it difficult to sufficiently exhibit the performance as the
synchronous reluctance motor.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a lateral cross sectional view of a rotary electric
machine according to an embodiment.
FIG. 2 is an expanded lateral cross sectional view of one magnetic
pole portion of the rotor of the rotary electric machine.
FIG. 3 is a diagram showing states of induction torque produced to
be compared with each other when flux barriers of respective
barrier regions of the rotor are filled with a nonmagnetic
conductive material.
FIG. 4 is a diagram illustrating a circle having a radius R and
circumscribing an outer circumference of a rotor core and a
hyperbola g of a proportionality factor a.
FIG. 5 is a diagram showing a relationship between induction torque
and reluctance torque in the case where a barrier region is
provided in only one layer, which is the outermost layer.
FIG. 6 is a diagram showing a relationship between the induction
torque and reluctance torque in a rotor in which a barrier region
is provided in a plurality of layers.
FIG. 7 includes cross sectional views of one magnetic pole portion
of a rotor core in the cases where the barrier region in the
outermost layer is changed variously from one location to another
in the rotor in which the barrier region is provided in a plurality
of layers.
FIG. 8 is an enlarged lateral cross section view of one magnetic
pole portion of the rotor.
DETAILED DESCRIPTION
Various embodiments will be described hereinafter with reference to
the accompanying drawings. In general, according to one embodiment,
a rotor of a rotary electric machine, comprises: a shaft rotatable
around a central axis; and a rotor core comprising a plurality of
magnetic poles arranged in a circumferential direction around the
central axis, and coaxially fixed to the shaft. When, in a lateral
cross section of the rotor core, normal to the central axis, an
axis extending through a boundary between adjacent magnetic poles
and the central axis is defined as a d axis and an axis
magnetically intersecting perpendicular to the d axis is defined as
a q axis, the rotor core comprises a plurality of layers of barrier
regions formed to be arranged in a radial direction with intervals
respectively therebetween, in the plurality of magnetic poles, and
the plurality of barrier regions each comprises a flux barrier
extending from near a part of an outer circumferential surface of
the rotor core through the d axis to near another part of the outer
circumferential surface, a first bridge portion formed of an iron
core located between one end of the flux barrier and the outer
circumferential surface and a second bridge portion formed of an
iron core located between an other end of the flux barrier and the
outer circumferential surface, and at least a flux barrier of a
barrier region provided at an outermost circumferential surface
side being filled with a nonmagnetic conductive material. When a
radius of a circle circumscribed on the outer circumferential
surface is represented by R and an equation of a hyperbola X
coordinates and Y coordinates of which are two q axes adjacent to
each other in the circumferential direction is defined as xy-a=0, a
barrier-side edge on a side of the central axis, which defines the
flux barrier of the barrier region provided in an outermost
circumferential surface side is located within a range of
0.55<2a/R.sup.2<0.84.
Note that the disclosure below is given as merely exemplary. A
person skilled in the art could easily conceive to appropriately
modify within the spirit of the invention, and it is a matter of
course that all of modifications belong to the scope of the
invention. In addition, the drawings may schematically illustrate
widths, thicknesses, and shapes of the respective parts compared to
the actual appearance in order to make the explanation more clear,
but these are given as merely exemplary. The interpretation of the
invention should not be limited to the drawings. In the
specification and the drawings of this application, the same symbol
will be attached to the same element described already in the
previous drawings, and the detailed description will be
appropriately omitted.
EMBODIMENT
FIG. 1 is a lateral cross sectional view of a rotary electric
machine according to an embodiment, and FIG. 2 is an expanded
lateral cross sectional view of one magnetic pole portion of the
rotor of the rotary electric machine.
As shown in FIG. 1, a rotary electric machine 10 is configured, for
example, as an inner rotor type rotary electric machine, and an
annular or cylindrical stator 12 supported by a fixation frame (not
shown) and a rotor 14 supported inside the stator so as to be
rotatable around a central axis C and coaxial with the stator 12.
In the embodiment, the rotary electric machine 10 constitutes a
self-starting reluctance motor.
The stator 12 comprises a cylindrical stator core 16 and an
armature coil 18 wound around the stator core 16. The stator core
16 is formed by laminating a number of annular electromagnetic
plates of a magnetic material, for example, silicon steel in a
coaxial manner. The stator core 16 can as well be formed by
pressing soft magnetic powder. In an inner circumferential portion
of the stator core 16, a plurality of slots 20 are formed. The
slots 20 are arranged along a circumferential direction at regular
intervals. Each slot 20 is opened in an inner circumferential
surface of the stator core 16, and extends out in a radial
direction from the inner circumferential surface. Moreover, the
slots 20 each extend over full length along the axial direction of
the stator core 16. With the plurality of slots 20 thus formed, an
inner circumferential portion of the stator core 16 constitutes a
plurality of (for example, forty eight in this embodiment) stator
teeth 21 facing the rotor 14. The armature coil 18 is embedded in
the slots 20, and would around respective stator teeth 21 each via
an insulator or an insulating coat (not shown). As current is
allowed to pass through the armature coil 18, a predetermined flux
linkage is produced in the stator 12 (stator teeth 21).
The rotor 14 includes a cylindrically shaped shaft (rotation shaft)
22 and a cylindrically shaped rotor core 24 fixed at substantially
an axial center of the shaft 22 so as to be coaxial therewith. The
shaft 22 is rotatably supported around the central axis C with a
bearing (not shown). The rotor 14 is placed inside the stator 12 so
as to be coaxial therewith with a slight gap (air gap)
therebetween. An outer circumferential surface of the rotor core 24
opposes an inner circumferential surface of the stator 12 with a
slight gap therebetween. The rotor core 24 comprises an inner hole
25 formed to be coaxial with the central axis C. The shaft 22 is
inserted to and fit with the inner hole 25 so as to extend
coaxially with the rotor core 24. The rotor core 24 is formed from
a lamination body in which a number of annular electromagnetic
plates of a magnetic material, for example, silicon steel are
laminated in a coaxial manner. The rotor core 24 can be formed by
pressing a soft magnetic powder.
In this embodiment, the rotor 14 is set to be multi-pole, for
example, quadrupole. In the rotor core 24, a direction normal to
the central axis C is referred to as a radial direction, and a
direction around the central axis C is referred to as a
circumferential direction. Further, axes each passing the central
axis C and also a respective boundary between respective adjacent
magnetic poles and extending in a radial direction or a diametrical
direction to the central axis C are referred to as a d axis, and
axes electrically and magnetically intersecting normal to the d
axis are each referred to as a q axis. Here, directions in which a
flux linkage produced by the stator 12 easily flows are set as the
q axes. The d axes and q axes are provided alternately along the
circumferential direction of the rotor core 24 and in predetermined
phases. One magnetic pole portion of the rotor core 24 is referred
to a region between an adjacent pair of two q axes (quadrant
circular angle region). Thus, the rotor core 24 is configured as
quadrupole (magnetic poles). A circumferential center of one
magnetic pole serves as the d axis.
FIG. 2 is a cross sectional view showing one magnetic pole portion
of the rotor, which is a quadrant circular region thereof. As shown
in FIGS. 1 and 2, the rotor core 24 comprises a plurality of, for
example, four layers of barrier regions 30a, 30b, 30c and 30d for
each magnetic pole. In each magnetic pole, the four layers of the
barrier regions 30a to 30d are arranged in the order from a central
axis C side to an outer circumferential surface side in the radial
direction (d axis direction) of the rotor core 24 with intervals
therebetween. That is, the barrier regions 30a to 30d each reach
from one location in the outer circumferential surface of the rotor
core 24 through the d axis to some other location of the outer
circumferential surface, and extend while curving in a convex
manner with respect to the central axis C. The plurality of barrier
regions 30a to 30d are formed respectively between a plurality of
magnetic paths through which the magnetic flux formed by the stator
12 passes, so as to separate the magnetic paths from each
other.
In this embodiment, the barrier regions 30a to 30d each comprise a
flux barrier (gap layer) 32 extending in a hyperbolic fashion
around the d axis as a center, a thin coupling portion (first
bridge portion) 32a formed from an iron core located between one
end and an outer circumferential surface of the flux barrier 32 and
a thin coupling portion (second bridge portion) 32b formed from an
iron core located between the other end and the outer
circumferential surface of the flux barrier 32.
For example, in the barrier region 30a provided in an innermost
circumferential side, one end of the flux barrier 32 is located
near the outer circumferential surface and also near one q axis and
the other end of the flux barrier 32 is located near the outer
circumferential surface and also near the other q axis. The flux
barrier 32 extends from the one end to the other end along the q
axes so that circumferential center thereof is located at the
radially innermost side while curving in a convex manner from the
outer circumferential side to the central axis C on a radially
inner side.
The barrier regions 30b, 30c and 30d of the second layer, the third
layer and the outermost layer are arranged along the d axial
direction with an interval between themselves and the barrier
region 30a of the innermost layer. Note that the barrier regions
may not necessarily be formed in four layers, but may be in two,
three layers, or in five or more layers. Further, each flux barrier
is not limited to one continuous layer but may be a plurality of
divided barrier layers.
At least in the flux barrier 32 of the barrier region 30d of the
outermost layer is filled with a nonmagnetic conductive material
such as aluminum or copper, thus forming a secondary conductor 34.
In this embodiment, the flux barriers 32 of the barrier regions 30a
to 30d of four layers are filled with a nonmagnetic conductive
material, thus forming the secondary conductors 34, respectively.
These secondary conductors 34 are short-circuited to each other
with a short-circuiting member (not shown) provided an axial end of
the rotor core 24, thus constituting a secondary coil.
As described above, a plurality of layers of barrier regions are
provided in substantially a hyperbolic manner. FIG. 3 shows
comparison among the secondary conductor regions in what degree of
induction torque is created thereby when the flux barrier 32 of
each barrier region is filled with a nonmagnetic conductive
material. As shown, the most of the induction torque is created in
the secondary conductor 34 in which the flux barrier 32 of the
barrier region 30d on the outermost circumferential side, which is
closest to the outer circumferential surface of the rotor 14 is
filled. This is because there is more interlinking q axis magnetic
flux in the secondary conductor 34 located closer to the outer
circumferential surface. That is, in order to increase the
induction torque, it is effective to enlarge the area of the flux
barrier 32 and fill the area with a nonmagnetic conductive
material. Now, to what extent the flux barrier 32 of the barrier
region 30d can be expanded will now be verified.
FIG. 4 illustrates a circle having a radius R, circumscribed on the
outer circumference of the rotor core, which can be expressed as:
f(x, y)=0, and a hyperbola to a proportionality factor a, which can
be expressed as: g(x, y)=0. In FIG. 4, it is assumed that X
coordinates and Y coordinates normal to each other correspond to q
axes, respectively. In FIG. 4, the circumscribed circle f and the
hyperbola g can be expressed as follows.
.function..function..times..times. ##EQU00001##
The area S of the region surrounded by these curves can be
calculated by the following formula.
.times..pi..times..times..times..function..times..times.
##EQU00002##
In the above formula, t=2a/R.sup.2 and t is a barrier constant.
From the condition that there is an area surrounded by f(x, y)=0
and g(x, y)=0, (there are two intersections), a relationship
0.ltoreq.t<1 is established.
Let us suppose the case where the circumscribed circle: f(x, y)=0
expresses the outer circumference of the rotor core, the region
surrounded by the circumscribed circle and the hyperbola g(x, y)=0
is the secondary conductor area, and the region defined by g(x,
y)<0 is an iron core portion. Here, it is considered that the
magnetic potential applied from the armature coil is distributed in
substantially a sine wave shape, and the density of the flux
generated in the gap between the inner circumference of the stator
and the outer circumference of the rotor is also distributed in
substantially a sine wave shape. Therefore, the flux density
B.sub.q of the gap in the case where the q axis magnetic flux is
generated can be expressed as follows. B.sub.q.varies.B cos
2.theta. [Formula 3] where .theta. is a circumferential component
when expressed in polar coordinate. When, of the intersections of
the functions f(x, y)=0 and g(x, y)=0, the one close to the x axis
is assigned as A, it can be expressed as: (r, .theta.)=(R,
(sin.sup.-1)/2) in polar coordinate. Therefore, the q axis magnetic
flux .PHI..sub.q is proportional to the result of integrating
B.sub.q toward the intersection
A from the x-axis.
.PHI..varies..intg..times..times..times..times..times..times..theta..time-
s..times..times. ##EQU00003##
If the q axis magnetic flux .PHI..sub.q changes at an angular
velocity .omega., an induction voltage V is generated in the
secondary conductor area by the Faraday's law. V=.omega..PHI.q
[Formula 5]
Here, the resistance of the secondary conductor area is inversely
proportional to the area S of the secondary conductor area, and
therefore a current I flowing in the secondary conductor area can
be expressed as follows.
.varies..times..varies..times..pi..times..function..times..times.
##EQU00004##
An induction torque T.sub.m generated at this time is proportional
to the current I and the magnetic flux .PHI..sub.q, the formula can
be rewritten as follows.
.varies..times..pi..times..function..times..times. ##EQU00005##
Next, a reluctance torque T.sub.r is focused. The reluctance torque
T.sub.r is produced due to the difference between the magnetic flux
of the d axis and the magnetic flux of the q axis. When the d-axis
magnetic flux .PHI..sub.d is calculated in a similar manner to that
of the q-axis magnetic flux .PHI..sub.q, the following relationship
can be obtained.
.PHI..varies..intg..times..times..times..times..times..times..theta..intg-
..times..times..times..times..times..times..times..theta..times..times..ti-
mes..times..theta..times..function..times..times..times.
##EQU00006##
Therefore, the reluctance torque T.sub.r can be expressed as
follows. T.sub.r.varies..PHI..sub.q-.PHI..sub.d.varies.t-1+cos
(sin.sup.-1t) [Formula 9]
FIG. 5 illustrates T.sub.m and T.sub.r, in which the maximum values
of T.sub.m and T.sub.r are respectively standardized. As shown in
FIG. 5, the induction torque T.sub.m becomes a maximum when t=0.55,
and the reluctance torque T.sub.r becomes a maximum when t=0.71.
Therefore, theoretically, when the barrier region 30d is disposed
to satisfy t=0.71, the induction torque T.sub.m can be maximized
without lowering the reluctance torque T.sub.r. Moreover, when it
is set as t=0.55, the induction torque T.sub.m can be maximized
while suppressing the lowering of the reluctance torque T.sub.r to
a minimum level. Thus, it depends on whether such a design that the
priority is given to the reluctance torque (steady
characteristic-oriented) or such a design that the induction torque
is maximized (starting characteristic-oriented) should be taken, it
is desirable to use t properly in a range of 0.55<t<0.71.
Note that when considered as an arc ratio .theta., (as in the case
of JP 4588255 B, the barrier constant t can be converted as
follows.
.theta..pi..times..times..times. ##EQU00007##
Therefore, t=0.55 corresponds to .theta.=57 degrees, t=0.71
corresponds to .theta.=45 degrees, and t=0.84 corresponds to
.theta.=33 degrees.
The discussion made so far is based on a theoretical study for the
case where the barrier region is provided in one layer of the
outermost circumferential layer, as shown in FIG. 4. However,
usually, a plurality of layers of barrier regions are provided to
further increase the reluctance torque. More specifically, as in
this embodiment, the barrier regions 30c, 30b, 30a and the like are
provided at locations closer to the central axis C as compared to
the barrier region 30d. In this case, the reluctance torque is
generated not only by the barrier region 30d but also by the
barrier regions 30c, 30b and 30a. Thus, it is expected that the
value of the barrier constant t which maximizes the reluctance
torque may change from 0.71.
Under these circumstances, the torque for the case where only the
barrier region 30d of the outermost layer is changed in the
structure including the the barrier regions 30d, 30c, 30b and 30a
was calculated by the magnetic field analysis. FIG. 7, which
includes parts (a) to (d), shows cross sections of one magnetic
pole portion of the rotor core when the barrier region 30 was
changed in variously manners. As shown, the region occupied by the
barrier region 30a becomes greater as the barrier constant t
becomes less. For example, FIG. 7, part (a) shows the cross section
when t=0, and FIG. 7, part (d) shows the cross section when
t=0.7.
FIG. 6 shows the results of the analysis of the torque. Note in
FIG. 6, the phase angle of the current was changed for a fixed
barrier constant t, and the calculation was performed to acquire
values obtained in a phase in which the torque becomes the maximum,
which are plotted in the graph. Thus, when a plurality of layers of
barrier regions (flux barriers) are provided, the reluctance torque
T.sub.r is generated by the barrier regions 30c, 30b and 30a under
the condition of t=1, by which the barrier region 30d vanishes.
Therefore, the reluctance torque becomes the maximum when t=0.84,
which is greater than the value t=0.71 obtained when there is only
one layer of barrier region provided, by a theoretical calculation.
As a result, the set value of the optimal barrier constant t is
defined as 0.55<t<0.84. When the efficiency of the reluctance
torque is considered to be critical, it is desirable to place the
set value of the barrier constant t (2a/R.sup.2) to satisfy:
0.55<t<0.78.
As shown in FIG. 8, the flux barrier 32 of the barrier region 30d
of the outermost layer is defined between the inner
circumferential-side edge (barrier-side edge) 35a and the outer
circumferential-side edge 35b opposing thereto with a gap
therebetween. Then, the flux barrier 32 is formed so that the inner
circumferential-side edge (barrier-side edge) 35a is located in the
region between the hyperbola when t=0.84 and the hyperbola when
t=0.55. Thus, such a rotor of a rotary electric machine which can
increase the induction torque T.sub.m without decreasing the
reluctance torque T.sub.r can be obtained.
Note that when the number of layers of barrier regions is changed,
pulsation components including a torque ripple greatly change, but
the average torque which contributes to the actual output does not
significantly change. In other words, in this embodiment, there are
four layers of barrier regions are provided, but it is considered
that a similar tendency to that described above can be obtained if
three or less layers or five or more layers are provided.
Moreover, the shape of the inner circumferential-side edge
(barrier-side edge) 35a of the flux barrier 32 may not necessarily
be a perfect hyperbola. More specifically, it suffices if the inner
circumferential-side edge 35a of the flux barrier 32 extends within
a region of a range of 0.55 to 0.84 described above, and it may be
a polygonal shape such as bath tub-like or a shape approximated to
a circle.
While certain embodiments have been described, these embodiments
have been presented by way of example only, and are not intended to
limit the scope of the inventions. Indeed, the novel methods and
systems described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the methods and systems described herein may be made
without departing from the spirit of the inventions. The
accompanying claims and their equivalents are intended to cover
such forms or modifications as would fall within the scope and
spirit of the inventions.
The above-provided embodiment is directed to a quadrupole rotor,
but it is not limited to this. For example, the rotor may be of a
dipole type or of a six magnetic pole type. The number of poles of
the rotor, the size, shape, the number of layers of barrier
regions, and the like are not limited to those of the embodiment
described above, but may be variously changed according to the
design.
* * * * *